Baseline survey of anthropogenic pressures for the Lac Bay ecosystem, Bonaire IMARES

Transcription

1 Baseline survey of anthropogenic pressures for the Lac Bay ecosystem, Bonaire Adolphe O. Debrot, Carsten Wentink, Astrid Wulfsen Report number C092/12 IMARES Wageningen UR Institute for Marine Resources & Ecosystem Studies Client: The Ministry of Economic Affairs, Agriculture and Innovation Paul C. Hoetjes, Policy Coordinator Nature P.O. Box 20401, 2500 EK The Hague, The Netherlands BO Publication date: 24 July, 2012

2 IMARES is: an independent, objective and authoritative institute that provides knowledge necessary for an integrated sustainable protection, exploitation and spatial use of the sea and coastal zones; a key, proactive player in national and international marine networks (including ICES and EFARO). This report is part of the Wageningen University BO research program (BO ) and has been financed by the Ministry of Economic Affairs, Agriculture and Innovation (EL&I) under project number P.O. Box 68 P.O. Box 77 P.O. Box 57 P.O. Box AB IJmuiden 4400 AB Yerseke 1780 AB Den Helder 1790 AD Den Burg Texel Phone: +31 (0) Phone: +31 (0) Phone: +31 (0) Phone: +31 (0) Fax: +31 (0) Fax: +31 (0) Fax: +31 (0) Fax: +31 (0) imares@wur.nl imares@wur.nl imares@wur.nl imares@wur.nl IMARES Wageningen UR IMARES, institute of Stichting DLO is registered in the Dutch trade record nr , BTW nr. NL The Management of IMARES is not responsible for resulting damage, as well as for damage resulting from the application of results or research obtained by IMARES, its clients or any claims related to the application of information found within its research. This report has been made on the request of the client and is wholly the client's property. This report may not be reproduced and/or published partially or in its entirety without the express written consent of the client. A_4_3_2-V of 71 Report number C092/12

3 Contents Terms of reference... 5 Summary Introduction Objectives Area description Methods Results Lac watershed catchment area Activities in the wider watershed area Businesses operating at Lac Activities around the bay Man-made litter in Lac Bay Traffic densities along the mangrove route (Kaminda di Sorobon) Other disturbance in the mangrove-zone Fishing activity How Sorobon beach goers experience crowding User awareness Discussion Conclusions and recommendations Literature cited Quality assurance Justification Appendix A. Cruise schedule and monitoring days Appendix B. Monitoring sheet human activity Lac Bay Appendix C. Questionnaire for Lac Bay beach goers Appendix D. Questionnaire for Taxi drivers Report number C092/12 3 of 71

4 Appendix E. Questionnaire for Kunuku owners Appendix F. Interviews stakeholders Lac of 71 Report number C092/12

5 Terms of reference The mangrove and seagrass lagoon of Lac Bay on Bonaire covers an area of roughly 700 ha. It is home to endangered green sea turtles, Chelonia mydas, and the Caribbean queen conch, Strombus gigas, and is an important roosting site for birds. Other endangered species include the threatened corals Acropora palmata and A. cervicornis and the rainbow parrotfish, Scarus guacamaya and some other IUCN vulnerable species. Based on its nature values this 7km 2 bay has been designated as a legally protected Ramsar site (Stinapa Bonaire 2003) and identified as a Birdlife International IBA (Important Bird Area) (Wells and Debrot 2008). The area falls under the management responsibility of the National Parks Foundation of Bonaire STINAPA Bonaire which tries to address several based on a 2009 management plan. Lac Bay is under increasing development pressure for recreational use and more-effective management is clearly necessary. As a Ramsar area, several international obligations need to be met, including the documentation of changes, management according to wise use and regular reporting. Based on concerns about Lac and the international commitments, in 2010 the then Ministry of LNV, The Netherlands, commissioned IMARES to assess the situation (Debrot et al. 2010a) and come with a shortlist of action points (Debrot et al. 2010b) that address the principal information gaps. This ministry (today the Ministry of Economic Affairs, Agriculture and Innovation, or EL&I) continues to actively exercise its mandate with respect to the biodiversity of the Caribbean Netherlands and commissioned this study. One of the identified information gaps was the need to quantitatively document and assess the current level of user pressures on the Lac ecosystem and such is the subject of this contribution. We like to thank the following people for their generous assistance, information and cooperation: Frank van Slobbe from the Department of Environment and Natural Resources (DROB) for assistance with the required permits, and Dr. Rita Peachy from CIEE Bonaire for allowing us to use her laboratory. Ton Akkerman and Hayo Haanstra of EL&I arranged the funding required for our work. This work was done under auspices of and in close cooperation with Stinapa Bonaire. We particularly thank Bonaire Marine Park Manager, Ramon de León for his all-around support and assistance. Washington-Slagbaai Park Manager, Juny Janga and the rest of the staff and personnel at STINAPA Bonaire are thanked for their advice and help. Geoconsult generously provided us their 2011 traffic data for Kaminda di Sorobon, while Domeinbeheer gave information on the distribution of kunuku s, and Mr. R. Emers provided information on animal husbandry. Sabine Engel, Paul Hoetjes, Ramon de León, Diana Slijkerman and Mabel Nava, are thanked for providing supplemental information and valuable reviews. Dr. Erik Meesters assisted with the software with which the catchment area was estimated. Alwin Hylkema and Willem Vogelaar helped collect beach litter data. Finally, Peter Smit and François Perreau of the van Hall- Larenstein College are thanked for fulfilling their role as student advisors for Carsten and Astrid. Report number C092/12 5 of 71

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7 Summary Lac Bay of Bonaire is a shallow non-estuarine lagoon of about 700 hectares, separated from the open sea by a shallow coral barrier-reef. It possesses the only major concentration of seagrass beds and mangroves of the island. It is a designated Ramsar wetland of international significance, an Birdlife International IBA (Important Bird Area) and also fulfills a critical fish nursery function for the reefs of the island. The bay has consequently been designated as a protected area and is managed by Stinapa- Bonaire. The bay has been losing effective seagrass nursery habitat surface and quality as a consequence of mangrove-driven land acclamation. This in-turn is potentially being exacerbated by human-mediated eutrophication and erosion caused by agricultural and animal husbandry in the wider watershed, as well as other factors. The number of visitors to Bonaire and to Lac has been increasing dramatically over the last decades particularly from cruise ships. Yet little has been done to document and map the various types of human use that occur on and in the vicinity of the bay which might affect the ecological carrying capacity of the bay and the critical roles it plays. In this survey we do preliminary mapping and analysis of the level and distribution of human activity in and around Lac and discuss what possible threats these may entail for the environment of the bay. The Lac catchment area was mapped using satellite imagery combined with field verification and gave a preliminary estimated size of about 22.6 km 2 of surrounding lands. This area consists of a mix of seminatural deciduous and dry-evergreen vegetation types and at least 213 small part-time amateur farms (for seasonal planting and animal husbandry). Fresh water surface-flow from the hinterlands to the bay is also affected by approximately 54 dams, and groundwater extraction by many (uncounted) wells. A review of local sources as supplemented by field observations indicate that extensive livestock husbandry (goat and sheep), occurs at densities higher than 1 animal per hectare. Such densities well exceed densities (as found from practice in Curaçao) that permit ecological recovery (0.1 animal per hectare). Therefore, in the natural areas surrounding Lac measures to reduce livestock densities are recommended. The major recreational activities at Lac are sunbathing, windsurfing and swimming or wading. Other aquatic activities include kayaking, snorkelling and fishing. Beach visitor distribution, densities and activity were monitored for 31 days at Lac during the spring tourist season of 2011 (March April). In addition we interviewed beach visitors, taxi drivers and recreational part-time farmers that plant and keep livestock in the greater Lac watershed area to assess their level of understanding, concerns and potential support for various measures. The majority of recreational use of Lac is concentrated on and around the Sorobon Peninsula. While Lac stands out for its international biodiversity value and its legal status as a Ramsar wetland, relatively little current use was directed towards nature activities (such as snorkelling, diving, hiking, sportfishing, kayaking, birding etc.). Visitor numbers present on the Sorobon beach at different times of the day differed depending on whether a cruise ship was in port or not and whether it was a week- or weekend day. Average peak visitor numbers at Sorobon on days with cruise ships in port was 359 people. On week days it was 187 people while on weekends it was 260 people. Usage patterns and awareness differed importantly between the four different user-categories of cruise tourists, stay-over tourists, foreign residents and inhabitants born on Bonaire. The effect of crowding had negative effects on the quality of experience of the beach visitors, and the majority of businesses operating at the bay believe that the large and growing number of cruise ship visitors needs to be curtailed. While only 9.7% of respondents felt that more hotel capacity at Lac was to be desired, this was almost fully compensated by 8% who felt that less hotel capacity would be better. Notwithstanding high awareness of the purpose of marker lines placed by the Sea Turtle Club of Bonaire to protect the near-shore seagrass beds of Sorobon, the inner borders of the seagrass exclosures Report number C092/12 7 of 71

8 displayed much bare space due to trampling. The problem of seagrass trampling had been documented by others before and clearly remains an issue. Trampling of the seafloor in the shallows of Sorobon outside of the seagrass-exclosures is intensive and may strongly limit seagrass coverage in these shallow areas. Also, some 7% of windsurfers make incursions into surfer-excluded areas near mangroves and over the seagrass shallows, while some 14% further state to have seen one or more sea turtles while on the water. Based on our own observations, and as confirmed by M. Nava (pers. comm.), sea turtles in the bay generally react strongly to boats and surfers. The possibility that disturbance, along with other factors such as habitat selection and food density, affect the distribution of turtles in the bay cannot be excluded. Interviews with entrepreneurs indicate that many of the used septic tanks are of old age and leaking. Untreated nutrient- and bacteria-rich septic water is being used for irrigation of ornamental gardens. As there is no sewage treatment and as the available toilets and cesspits are generally defunct, beach visitation definitely result in nutrient enrichment in the waters of the bay where Slijkerman et al. (2011) have already documented eutrophication as a problem. Beach litter contamination is a matter of concern in two areas within Lac. These are the areas down-wind from the entrance of the bay which have high concentrations of beach litter along mangrove shores and the lagoon-bottom immediately off the public beach of Sorobon. The mangrove area has the most serious litter contamination problem, where its source is largely distant (drifts in) and more household in character. At Sorobon the source of the submerged beach litter is local, and its nature is recreational. Submerged litter densities at the public beach of Sorobon is at levels comparable to unmanaged beaches in Curacao. Additional data on the apparently reduced level of fishing and negative effects of vehicular traffic are presented and discussed. From this and other studies it is clear that the combined levels of anthropogenic impact on the bay currently exceed sustainable levels. Additional problems, possibly exacerbated by the cumulative effect all the different anthropogenic stressors, are the rapid invasion of the exotic seagrass, Halophila stipulacea and a bloom of an encrusting (possibly invasive) calcareous alga (Ramicrusta sp.) that is smothering live corals at the seaward side of the bay. Based on the ecological importance of the bay, its legal status as designated Ramsar site, the various ecological problems that have been fairly documented, as well as the negative effect of current peak crowding levels on the visitor experience itself, it is recommended to develop beach options for cruise ship tourists elsewhere on the island and/or to create or better-promote other activities for the cruise tourist to engage in. Also, roaming livestock levels in the vicinity of the bay should be reduced, either structurally by introducing husbandry management in the surrounding areas or locally by grazer exclusion (fencing). In addition, various measures (most of which have already been recommended by others) can be taken on-site to reduce visitor impacts, and enhance visitor experience. Firstly, the user facilities and infrastructure at Lac need to be upgraded. These would include the toilets and septic systems, garbage disposal, organized parking, availability of shade, signage and marker buoy-lines for the various management zones. Implementing a Lac Visitor Centre to provide visitor service (products and addedvalue information) and enforcement, could also contribute to visitor s awareness of the unique natural values of the Lac area and of the zoning plan. We list additional management suggestions with which to address specific issues and identify several knowledge gaps meriting further study. This report is part of the Wageningen University BO research program (BO ) and has been financed by the Ministry of Economic Affairs, Agriculture and Innovation (EL&I) under project number of 71 Report number C092/12

9 1 Introduction Lac Bay is a designated Ramsar wetland of international significance (Ramsar Convention 2011) and a Birdlife International IBA (Important Bird Area) (Debrot et al. 2010a). In this non-estuarine, clear-water bay area, multiple types of habitats can be found. Around the bay three types of mangrove vegetation can be found, (red mangrove, Rhizophora mangle, black mangrove, Avicennia germinans and white mangrove, Laguncularia racemosa), as well as the green buttonwood (Conocarpus erectus) (Debrot et al. 2010a). The mangroves of Lac show clear zonation and succession with principal seaward zone of Rhizophora, and principal landward zone of Avicennia and depending on the location, an intermediate mixed transitional zone (Davaasuren and Meesters 2012). A large part of the sandy seabed of the bay is covered by seagrass. The turtle seagrass, Thalassia testudinum, is an important food source for the protected Green Turtle (Chelonia mydas). It is also a habitat for the endangered Caribbean Queen Conch, Strombus gigas. Also the Rainbow Parrotfish (Scarus guacamaya) can be found here, as well as some other IUCN red list species. Lac Bay is one of the most important natural areas on Bonaire as it serves as nursery habitat for many economically and ecologically important coral reef species. Rather extensive background studies and inventories for Lac have been provided by Moorsel and Meijer 1993 and Lott 2001). Tourism is one of the most important driving forces behind the Caribbean economy (Goodwin 2008). However, this economic contribution comes with a price. Damage to coastal habitats is caused by uncontrolled development of marine recreational activities, marine water contamination and solid waste generation. As a result, the carrying capacity of such areas can be exceeded and in some cases impacts are irreversible (EC 2007). Tourism numbers at Bonaire are much lower than at many other Caribbean destinations (CTO 2011), but over the past decades the number of visitors has been increasing (Bonaire Tourism Corporation 2009). Most cruise tourists wishing to spend time on a beach are taken to Lac and the large increase in tourists visiting the bay is expected to influence the ecology of the bay and the quality of the experience for the visitors. As mangrove ecosystem health and development is greatly determined by salinity and nutrient fluxes, and by freshwater streaming into the system from afar, a watershed perspective is needed in managing and limiting anthropogenic impacts on the bay ecosystems. For this reason we not only studied activities on the bay itself but also mapped the watershed and provided an initial assessment of activities that take place farther away from Lac but which still likely or potentially affect its ecology. Report number C092/12 9 of 71

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11 2 Objectives The objectives of this study were document through observation the kinds of use, number of users, and where these activities are taking place in relation to the present nature values and the current zoning plan. We also used questionnaires to assess the level of awareness, perceived needs and willingness to cooperate of various groups using the bay or the hinterlands. While we do comment on the potential effects these activities might have on the biota of the bay, we did not measure or compare these effects, as doing such would require much more extensive and in depth study. Report number C092/12 11 of 71

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13 3 Area description Lac Bay is located along the eastern coast of Bonaire and covers an area of roughly 700 hectares. The bay is largely 0-3 m deep and protected from the waves of the wind-exposed eastern coast by a shallow coral barrier-reef. The main channel connecting the bay to the sea and the luxuriant fringing reef that surrounds the island is about 5 m deep. Apart from the sediment-ridden, murky backwaters, various levels of seagrass and algal development can be found throughout the different sectors of the bay. The semidiurnal tidal amplitude in this part of the southern Caribbean averages about 30 cm (de Haan and Zaneveld 1959), which, along with the shallow depth of large sections of the bay, translate into low circulation. The bay forms part of the Bonaire National Marine Park which extends to a depth of 60 meters surrounding the whole island, and which also includes the island of Klein Bonaire (STINAPA 2009). Fig. 1. Map of Bonaire showing the location of Lac (STINAPA, 2003) The area around the bay is often used for seasonal agricultural purposes and extensive animal husbandry. At the Sorobon peninsula (Fig. 2) a large sandy beach is found which makes a suitable place for sunbathing and swimming. Lac is also a popular place for windsurfing, snorkelling and kayaking. Two hotels are located at Lac. These are Sorobon Beach Resort and the Kontiki Beach Club. Next to Sorobon Beach Resort there are two beach bars, Jibe City Beach Bar and The Beach Hut. Also two windsurfing Report number C092/12 13 of 71

14 centres are located here; The Windsurf Place and Jibe City. Over the past years Bonaire has seen a large increase in visitor numbers. From 2001 to 2008 stay-over tourism grew from about 50,000 to 74,000 visits annually, while cruise tourism grew from 40,000 to 176,000 visits annually (Bonaire Tourism Corporation 2009). The tourism sector hopes to see continued growth in visitor numbers in the future (Bonaire Tourism Corporation 2009) and many hotel projects remain to be completed. The Sorobon peninsula is especially visited by many cruise tourists, who are dropped-off at the beach and only stay for a fewl hours. Also, foreign residents and locals from Bonaire visit the place for work or recreational purposes. All these visitors to greater or lesser extent interact with nature by disturbing the wildlife and touching, collecting or walking over seagrass and coral reefs or leaving litter or other forms of pollution behind (Kats 2007). Fig. 2. The Sorobon peninsula of Lac, showing the location of the user facilities mentioned in the text. 14 of 71 Report number C092/12

15 4 Methods Mapping the watershed and land-use at the landscape level Field data collection on Bonaire principally took place in the period April May The catchment area of Lac was defined with the usage of the software Quantum GIS with a GRASS GIS plug-in. In this software a map with DEM data at Bonaire was used. In this map the differences in topographic heights can be determined. These heights were used in determining the directions of surface water flows in the area. The combination of heights and the directions in which water flows provided the information needed to determine the actual catchment area. Aerial photographs and cadastral maps provided a starting point for mapping of human land use in the catchment area around Lac. Particular focus was on structures meant for water extraction (wells) and water diversion or catchment (irrigation dams), fields and enclosures (often cleared or ploughed for planting), presence of livestock etc. Businesses centered at the bay Private businesses, such as dive schools, windsurf centers and hotels not only facilitate visitor use of the Lac area, but in and of themselves represent important anthropogenic pressure to the Lac area. The main businesses operating and causing potential environmental pressures in the area were listed and discussed. Surveying recreational user distribution and densities Monitoring of the number of people engaged in different activities in the bay was done for a 31 day period, from March 4 - April 27, Cruise ships were in port for 14 of the 31 days, and 12 of these concerned weekdays. We compared and contrasted beach visitor numbers between cruise-ship days (N = 14) versus ordinary week days (N = 9) and ordinary weekends (N = 8). An overview of the monitoring days and the cruise schedule can be found in Appendix A. Every 1.5 hrs, from 9 am to 6 pm, the number of people engaged in different activities in different parts of the bay were recorded and mapped in relation to the various management zones. Monitoring took approximately 5-15 minutes a time, depending on the number of visitors. This data was recorded on monitoring sheets (Appendix B). No structural monitoring was carried out at Cai due to the relatively low and generally predictable level of recreational use as established during several visits. Apart from limited fishing activity, practically all water based recreation originates from the Sorobon peninsula. For this reason it was decided that Sorobon is most suitable for carrying out monitoring and survey activities. In this, Sorobon provided the best vantage point from which to oversee almost all of the bay (except the mangrove creeks on the north side of the bay). Man-made litter in Lac Bay One key anthropogenic impacts in the marine environment is contamination. This may take various forms, one important one of which is marine litter pollution. Marine litter contamination affects ecosystems and the provision of ecosystem services in various ways, among which deleterious effects on wildlife, habitat quality, economy, aesthetics, human health and even safety (UNEP 2006). It is a widespread problem and is considered to be one of the most serious threats to sustainable use of the region s marine and coastal resources (UNEP 2006). To assess this issue for Lac, in October 2011 we sampled litter pollution at three mangrove beach sites at Punta Kalbas opposite and down-wind from the entrance of Lac Bay, and two submerged transects directly off the public beach at Sorobon. Report number C092/12 15 of 71

16 The beach transects sampled in mangrove forests were 5 meters wide and extended seawards from the last terrestrial vegetation (as is standard methodology for beach litter sampling (e.g. Debrot et al. 1999), straight out towards the sea and into the mangroves. Because the mangroves were difficult to penetrate for sampling, the three transects differed in the extent to which the mangroves were sampled. Transect lengths were, respectively: 2 m beach and 5 m mangroves, 4 m beach and 15 mangroves, and 5 m of beach (all 5 m-wide). All three transects were placed in areas of the bay with a relatively narrow mangrove fringe. Data on submerged beach debris were collected on October 4, 2011, in two 4-m wide x 25-m long transects parallel to the shore at 2-3 m depth in front of the Lac public beach at Sorobon (to the north side of the fishing pier). All material was collected and removed from the site for cleaning, counting, sorting, measuring and weighing in the lab. Results are expressed as number or weight of objects or materials per stretching meter of beachfront. Vehicular traffic in the mangrove zone of the bay Available data on traffic levels on the road that runs along the Lac mangroves generously provided by Geoconsult who had collected these data in 2010 for consultancy purposes. The traffic counts using pneumatic road tubes were made by Geoconsult in 2010 in front of the Kontiki Beach Club on one day with cruise ship traffic ( ) and one day without ( ). Index of fishing levels A survey of fishing boat abundance at Lac provide an index of fishing activity to be compared with data from the early 1990s by Moorsel and Meijer (1993). Seven bay-wide daytime boat counts of small open fishing boats were conducted by BNMP staff over a period of 3 weeks in May and June, User and stakeholder feedback Aside from collecting and recording various forms of data on anthropogenic stressors operating in the Lac watershed and bay area, we also designed and conducted opinion surveys among three categories of users to be able to better describe the users and assess their level of awareness, perceived needs for various facilities and management measures. These were a) beach visitors, b) taxi drivers and c) subsistence farmers. Beach visitors: The beach visitor surveys were conducted in the months March and April This is the peak of the cruise season, whereas May September no large cruise ships dock at Bonaire (Bonaire Tourism Corporation 2009). During March and April, approximately people visit Bonaire, (Bonaire Tourism Corporation 2009). A total of 614 beach visitors were interviewed using the Lac visitor questionnaire by taking 2-3 visitor questionnaires immediately after each scheduled activity survey to be able to link opinions to different user densities (Appendix C). Taxi drivers: Taxi drivers play an important role in transporting tourists from the cruise pier in Kralendijk to Sorobon. Upon request of the RCN, a taxi driver questionnaire was set up. Taxi s driving to Sorobon have two possibilities for which road to take, one road leading close along the mangroves (Kaminda di Sorobon), and the road from Belnem, crossing the area called Lima. Traffic on Kaminda di Sorobon can be expected to cause more impacts to Lac through noise, disturbance, exhaust and traffic casualties than the road via Lima. We principally aimed to determine which road the taxi drivers used, and whether the drivers would be willing to provide their clients with some form of supplemental information about the nature values of Lac (e.g. a brochure). A total of 18 registered taxi drivers that shuttle tourists between Kralendijk to Lac were spoken to at the main pier in Kralendijk, and 15 questionnaires were filled (Appendix D). 16 of 71 Report number C092/12

17 Part-time seasonal agriculture and animal husbandry: Information on agrarian land-use in the catchment area of Lac was gathered by interviewing kunuku owners who s land lies in the catchment area. They were asked about the numbers and kind of livestock they keep, if and what type of agriculture they perform, and information on any water management infrastructure they have on their land, such as dams and wells. A total of 17 kunuku owners were interviewed based on the questionnaire. Reaching these respondents was particularly difficult because the owners were rarely present on their land (Appendix E). Stakeholder interviews: Aside from the three groups queried via questionnaires, we also obtained feedback from various stakeholders by means of open interviews and a stakeholder meeting. Stakeholder feedback is not discussed separately in this report but the main points made by the stakeholders have been synthesized into our discussion and recommendations. Minutes of the interviews can be found in Appendix F. Stakeholders included were: Sea turtle conservation Bonaire, Jibe City, The Windsurf Place, Beach Bar, Kontiki Beach Club, Mangrove Info and Activity Center, the restaurant at Cai, Sorobon Beach Resort and several fishermen (Appendix F). Analysis and presentation of results: Due to limited funding we were only able to provide elementary descriptive analysis and presentation. No full statistical assessment of the results are given here. Report number C092/12 17 of 71

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